As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE ACCOMPLISHING APU DEPRESERVATION APU WOULD NOT START. GROUNDED-YES. APU BITE SHOWED MESSAGE 49-41011, NO FLAME SHUTDOWN. INITIATED B737-800 FIM 49-40 TASK 802. IGNITER NOT AUDIBLE. REPLACED IGNITER AND IGNITER LEADS, REF B737-800 AMM 4-41-51 AND 49-41-52. NO HELP FAULT REMAINS. REMOVED AND REPLACED APU IGNITION UNIT, PER AMM 49-41-31. OPERATIONS TEST GOOD, NO FAULTS NOTED.